1. Field of the Invention
The invention relates to a collection container assembly that includes a plurality of nested containers formed from different respective materials and provides an effective is barrier against water and gas permeability and for extending the shelf-life of assembly especially when used for blood collection.
2. Description of Related Art
Plastic tubes contain an inherent permeability to water transport due to the physical properties of the plastic materials used in manufacturing tubes. Therefore, it is difficult to maintain the shelf-life of plastic tubes that contain a liquid additive. It is also appreciated that deterioration of the volume and concentration of the liquid additive may interfere with the intended use of the tube.
In addition, plastic tubes that are used for blood collection require certain performance standards to be acceptable for use in medical applications. Such performance standards include the ability to maintain greater than about 90% original draw volume over a one-year period, to be radiation sterilizable and to be non-interfering in tests and analysis.
Therefore, a need exists to improve the barrier properties of articles made of polymers and in particular plastic blood collection tubes wherein certain performance standards would be met and the article would be effective and usable in medical applications. In addition, a need exists to preserve the shelf-life of containers that contain liquid additives. The time period for maintaining the shelf-life is from manufacturing, through transport and until the container is actually used.
The present invention is a container assembly comprising inner and outer containers that are nested with one another. The inner and outer containers both are formed from plastic materials, but preferably are formed from different plastic materials. Neither plastic material is required to meet all of the sealing requirements for the container. However, the respective plastic materials cooperate to ensure that the assembly achieves the necessary sealing, adequate shelf life and acceptable clinical performance. One of the nested containers may be formed from a material that exhibits acceptable vapor barrier characteristics, and the other of the containers may be formed from a material that provides a moisture barrier. The inner container also must be formed from a material that has a proper clinical surface for the material being stored in the container assembly. Preferably, the inner container is formed from polypropylene (PP), and the outer container is formed from polyethylene terephthalate (PET).
The inner and outer containers of the container assembly preferably are tubes, each of which has a closed bottom wall and an open top. The outer tube has a substantially cylindrical side wall with a selected inside diameter and a substantially spherically generated bottom wall. The inner tube has an axial length that is less than the outer tube. As a result, a closure can be inserted into the tops of the container assembly for secure sealing engagement with portions of both the inner and outer tubes. The bottom wall of the inner tube is dimensioned and configured to nest with or abut the bottom wall of the outer tube. Additionally, portions of the inner tube near the open top are configured to nest closely with the outer tube. However, portions of the inner tube between the closed bottom and the open top are dimensioned to provide a continuous circumferential clearance between the tubes. The close nesting of the inner tube with the outer tube adjacent the open top may be achieved by an outward flare of the inner tube adjacent the open top. The flare may include a cylindrically generated outer surface with an outside diameter approximately equal to the inside diameter of the side wall of the outer tube. The flare further includes a generally conically tapered inner surface configured for tight sealing engagement with a rubber closure.
The container assembly of the present invention achieves the required shelf life for medical applications. Furthermore, the inner container can be formed from a material that will exhibit appropriate clinical performance in the presence of the specimen and/or additives in the container assembly.
The container of the present invention substantially eliminates the complications of maintaining the shelf-life of plastic containers that contain liquid additives. In addition, the container of the present invention minimizes the rate of moisture loss from plastic containers that contain liquid additives.
The container of the present invention provides the means to deliver a higher quality plastic container product to the customer because liquid additive concentration, additive volume and additive solubility are better controlled.
Another notable attribute of the container of the present invention is that it will not interfere with testing and analysis that is typically performed on blood in a tube. Such tests include but are not limited to, routine chemical analysis, biological inertness, hematology, blood chemistry, blood typing, toxicology analysis or therapeutic drug monitoring and other clinical tests involving body fluids. Further, the container of the present invention may be subjected to automated machinery such as centrifuges and may be exposed to certain levels of radiation in the sterilization process with substantially no change in optical, mechanical or functional properties.
Most notably, is that the container of the present invention impedes the rate of water vapor transport from within the container interior and thus controls additive solution concentration and volume for containers containing a liquid additive.